Red Blood Cell Dynamics: The Contribution of Microgravity in the BIOMICS Project

The complexity of blood flows is an intense subject of research since the pioneering works of Poiseuille and through studies over a wide range of scales, from the single red blood cell to dense suspensions in capillary networks, using a large variety of techniques. The subtle effects that are responsible for the structure of blood flows in vessels can benefit from the use of microgravity platforms in order to suppress sedimentation that prevents precise measurements of red blood cell dynamics. The BIOMICS experiment was performed in the MASER11 and MASER12 sounding rockets and was preceded and followed by several parabolic flight experiments in which two important phenomena were investigated using red blood cells and biomimetic model systems like lipid vesicles: the lift forces that push red blood cells away from walls and hydrodynamic interactions between cells that contribute to spreading, mixing, and segregation of different cell types. Parabolic flights played a crucial role in the definition of the scientific questions, preliminary experiments, hardware development and testing, as well as the definition of protocols, and were central in an experimental program combining ground and flight experiments on different platforms

Standing wave in evaporating meniscus detected by infrared thermography

A standing wave has been detected in the evaporating meniscus formed on an organic liquid (acetone) inside a horizontally positioned capillary tube of 1mm internal diameter. The standing wave is believed to originate from the interaction between surface tension and gravitational forces. We found that the standing wave ensues only at the upper part of the meniscus interface where gravity and surface tension act in the opposite direction. This experimental observation is similar to standing waves observed in floating zones in microgravity but different from travelling waves reported recently in volatile drops; in both cases the waves are produced by temperature differences along a liquid-vapour interface. By employing InfraRed thermography, we recorded the temperature distribution of the meniscus interface, and we found that the first characteristic frequency of the standing wave is around 0.3Hz.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Reconnaissance de formes par corrélation :une approche modulaire basée sur l'algorithme de sélection automatique des fréquences spatiales

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Development of pattern recognition tools based on the automatic spatial frequency selection algorithm in view of actual applications

info:eu-repo/semantics/publishe

Three-dimensional Marangoni cell in self-induced evaporating cooling unveiled by digital holographic microscopy

info:eu-repo/semantics/publishe

Reduction in correlation-filter sensitivity to background clutter by the automatic spatial frequency selection algorithm.

We propose an automatic spatial frequency selection correlation filter that reduces the sensitivity to nonoverlapping noise or background clutter. This is achieved by inclusion of distorted versions of the reference images surrounded by nonoverlapping background clutter. Furthermore, we impose that the window functions of the reference images give response zero-correlation amplitudes. Simulation results are provided in the case of a two-class pattern-recognition problem and show that the results are appreciably increased. The results are compared with a normal automatic spatial frequency selection.Journal Articleinfo:eu-repo/semantics/publishe

Three-Dimensional Marangoni cell in self-induced evaporating cooling unveiled by µ-Particle Image Velocimetry and Digital Holographic Microscopy

µ-Particle Image Velocimetry has successfully been used to map the velocity fields on diametrical horizontal and vertical cross sections of a transparent glass circular tube of 900µm diameter filled with ethanol. A Digital Holographic Microscope has been used to trace the trajectory of a tracer particle inside the liquid phase of an evaporating meniscus formed at the mouth of a 1mm square borosilicate tube filled with ethanol. The Marangoni flow cells are due to the self-induced differential evaporating cooling along the meniscus interface that creates gradients of surface tension which drive the convection. The competition between surface tension and gravity forces along the curved meniscus interface disrupts the symmetry due to surface tension alone. This distorts the shape of the toroidal Marangoni vortex. This is clearly seen in the µ-Particle Image Velocimetry velocity maps. Thermocapillary instabilities of the evaporating meniscus are reported in the present work by analysing the trajectories of a tracer particle. It is found that the trajectory of the tracer makes different shaped three-dimensional loops and every four loops it returns to the first loop. By analysing several loops it was found that the characteristic frequency of the periodic oscillatory motion is around 0.125 Hz.info:eu-repo/semantics/publishe

Self-assembly of carbon nanotube-based composites by means of evaporation-assisted depositions: importance of drop-by-drop self-assembly on material properties

Carbon nanotubes and silica nanoparticles are allowed to self-assemble into a nanocomposite by first forming an aqueous suspension, then depositing one drop after the other and finally letting them evaporate. Two types of composites are prepared. One by forming alternate layers and the other by forming several layers of a pre-mixed suspension. The thickness, thermal and electrical conductivity of the composites are measured versus the number of depositions. The pre-mixed composites showed an increase in the values in both the parallel and perpendicular directions of both the electrical and thermal conductivities, making them suitable for electrodes or battery-like applications. The values of the electrical and thermal conductivities in the perpendicular direction for the first composite decrease and increase, respectively, while for the parallel direction the values are significantly constant. As such, they would be useful as electrical insulators for optimal cooling. Thickness measurements showed that the pre-mixed composite is the denser one, due to a better alignment of the carbon nanotubes.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Fin condensation in variable gravity environment

We report on a condensation experiment of pure HFE-7100 on a curvilinear brass fin of 16 mm height cooled from the base by a Peltier/heat pipe/heat sink assembly. The experiment has been carried out in variable gravity environment aboard the Airbus A300 Zero-G aircraft of the European Space Agency performing parabolic trajectories during which the gravity has been varied from 1g to 1.8g and eventually to 10-2 g. An afocal optical system has been developed to measure the condensate liquid film on the fin with an accuracy of around 6 μm. The temporal evolutions of the liquid film thickness along the fin is determined and used to deduce the local Nusselt numbers in various gravity conditions. The derived heat of condensation increases in hypergravity and decreases noticeably during microgravity. This means that in microgravity a condenser should be designed with a larger surface area than on ground. We have also noticed local troughs of the film thickness most likely due to manufacturing imperfections of the fin.SCOPUS: ar.jinfo:eu-repo/semantics/publishe